According to the U.S. Environmental Protection Agency (EPA), high volume and high velocity storm water runoff can erode soil within the open channels, drainage ditches, and swales, and on steep exposed slopes, increasing the transport of sediments into receiving orders. Water quality impacts of increased sediment load include the conveyance of nutrient and pesticide pollutants, disruption of fish spawning, and impairment of aquatic habitat.
Traditionally, hard armor erosion control techniques such as concrete blocks, rock rip rap, and reinforced paving systems have been employed to prevent soil erosion in these highly erosive areas. Although these measures can withstand great hydraulic forces, they are costly, and they do not provide the pollutant removal capabilities of vegetative systems.
Turf reinforcement mats (TRMs) enhance the natural ability of vegetation to permanently protect soil from erosion. TRMs are composed of interwoven layers of non-degradable geo-synthetic materials such as polypropylene, nylon and polyvinyl chloride netting, stitched together to form a three-dimensional matrix. They are thick and porous enough to allow for soil filling and retention. In addition to providing its scour protection, the mesh netting of TRMs is designed to enhance vegetative root and stem development. By protecting the soil from scouring forces and enhancing vegetative growth, TRMs raise the threshold of natural vegetation to withstand higher hydraulic forces on stabilization slopes, stream banks, and channels. In addition to reducing flow velocities, the use of natural vegetation provides particulate contaminant removal through sedimentation and soil infiltration, and improves the aesthetics of the site.
TRMs offer high shear strength, resistance to ultraviolet degradation, and resistance to chemicals found in soils. TRMs, unlike temporary erosion control products, are designed to stay in place permanently to protect seeds in soils and to improve germination. TRMs can incorporate natural fiber materials to assist in establishing vegetation. However, the permanent reinforcement structure of TRMs is composed of entirely non-degradable synthetic materials. A variety of ground anchoring devices can be used to secure TRMs, including: U-shaped wire staples, metal pins, and wood or plastic stakes. Appropriate ground anchoring devices are chosen based on site-specific soil and slope conditions.
The use of TRMs allows vegetative cover to be extended to areas where site conditions would otherwise limit it. This helps to establish and maintain a continuous vegetative cover throughout the applied area. TRMs can be applied to most sites or structures where permanent erosion control is required. This technology has been effectively used in both urban and rural areas and in a variety of climactic conditions. Although most effective when used in fully vegetative areas, TRMs have been used to prevent erosion even in arid, semi-arid, and high altitude regions with limited vegetative growth. In these areas, vegetation establishment is slow or difficult, and the TRM matrix is typically filled with native soils for protection.
TRMs are being used to control erosion and stabilize soil to control runoff from land disturbing activities with steep slopes, and to prevent scouring in storm water detention ponds, water storage ponds, small open channels, drainage ditches, and runoff conveyance systems within the parking lot medians, and along stream banks and shorelines.
In addition to their use for new construction projects, TRMs have been used to retrofit existing hard armor systems. In addition to improving water quality, TRMs can provide aesthetic enhancement, especially in areas lacking vegetative growth.
TRMs provide water quality benefits by allowing the growth of vegetation in areas where impervious conveyance systems would otherwise be used. In general, the performance of TRMs is closely tied to the vegetative establishment and growth. The performance of the TRM-lined conveyance system depends on the duration of the runoff event to which it is subjected.
Known TRM materials are woven in a pattern that when exposed to heat, creates a loft or three-dimensional structure. In some instances, the loft must meet a minimum thickness specification (for example, 0.25 inch) in order to be considered a TRM. The energy required for heating the material, as well as the additional equipment required for carrying out the heating process, add considerably to the expense of the product. Also, the material typically shrinks in the lengthwise and widthwise dimensions as the fibers contract during heat-treatment process to create the loft. Thus, a loom width wider than the desired final product width is typically required.
Known TRM materials also typically include a single fiber or end at the peak and valley points of the weave pattern, and provide inadequate compression resistance for some applications.
It is to the provision of an improved TRM product and manufacturing process that the present invention is primarily directed.